How Are Brain Tumors Diagnosed?

Brain tumors are often difficult to diagnose because their signs and symptoms may mimic those of other disorders. Symptoms will also vary according to the exact location of the tumor. For example, many childhood brain tumors cause vomiting. However, there are other much more likely causes of vomiting. It is therefore not unusual that a child with vomiting is seen by a gastroenterologist before the proper diagnosis is made. Parents (and pediatricians) often feel distraught that they did not make the diagnosis earlier, but hindsight is always 20/20. Most of the time, the relatively short delay in diagnosis is of no significance in terms of outcome.

You probably helped make your child’s diagnosis when you brought him or her to the doctor in response to some early signs of trouble. Many early signs are due to the effects ofraised intracranial pressure (ICP), brought on by the tumor’s size or location, blocking the normal flow of cerebrospinal fluid (CSF) from the brain.

If the tumor has blocked the flow of cerebrospinal fluid (CSF), the excess fluid builds up and causes a condition called hydrocephalus. The resulting raised ICP causes symptoms that may include headaches (particularly in the morning), nausea, vomiting, poor coordination, seizures, drowsiness, and, in infants, an increase in head size. Other symptoms of a brain tumor may include behavior changes, blurred vision, weakness in a limb or on one side of the body, speech problems, and difficulty with balance.

Spinal cord tumors can cause pain (especially at night when a child is at rest). Tingling or weakness in the arms or legs and loss of bladder or bowel control may occur. The symptoms are related to pressure of the tumor on a particular area of the spinal cord.

Once other diagnoses have been ruled out, the doctor will take a health history of your child and do several measures of neurological function. Often a neurologist is involved; he or she may order tests such as an electroencephalogram (EEG) , a computed tomography (CT) scan, and a magnetic resonance imaging (MRI) scan. Sometimes the pediatrician will order these tests directly. These tests are generally noninvasive but may require intravenous (IV) injection of a special dye (usually gadolinium) that makes the tumor stand out or “enhance” on film. If your child is unable to lie very still for the scanning procedures, he or she may be given a sedative orally or intravenously. An experienced doctor will often be able to determine the type of brain or spinal cord tumor from CT or MRI results, but sometimes an exact diagnosis cannot be made until a sample of the tumor is actually sent to the pathologist for study under the microscope. The results from the pathologist will be important to formulate a treatment plan. Germ cell tumors can be diagnosed from a blood and CSF sample; tectal gliomas, diffuse pontine gliomas, and optic glioma are diagnosed by imaging and do not require biopsy in most cases.